Method and apparatus for separating water from oil

ABSTRACT

A method and apparatus for separating water from oil includes creating a vacuum in a container so that oil which contains water and gas bubbles is drawn upward through a first section of the container. At the top of the first section, the oil impacts a baffle plate, thereby releasing water vapor. The oil then flows downward through an obstruction component in a second section of the container, thereby releasing additional water vapor.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for separatingwater from oil.

Oils are prone to be strongly invaded by water from leaking coolers,condensate in reservoirs, cleaning and steam leakages. Water may reduceviscosity, cause defects of the structural composition of the oil anddisturb/destroy additives in the oil. This will result in anaccelerating change of the oil (the oil forming water as a result ofageing) and bacterial growth and corrosion, resulting in reduced life ofthe oil and of the components in which it serves.

U.S. Pat. No. 5,211,856 discloses a method of separating water from oil,in which the oil to be separated is introduced in a heated condition ata predetermined temperature into a container subjected to a vacuum. Gaswhich is preheated to the temperature of the oil is introduced into theoil in the container to form gas bubbles rising through the oil whileabsorbing water vapor which, together with the gas in the bubbles, isreleased in the upper part of the column and withdrawn from the topthereof.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a continuousseparation process which, by means of a particularly simple and reliableapparatus, results in a higher efficiency than that of the above andother prior methods of this type. In other words, in a simple manner,the process enables larger amounts of water to be separated per unittime from a certain amount of oil. This object is achieved according tothe invention, by a process and apparatus as defined in the claims.

Admittedly, it is a well-known technique to promote evaporation of aliquid by causing it to flow across a large surface area such as packingin a column. However, the present invention provides a surprisinglysimple and effective manner of combining the two above-mentioned priorseparating principles which, as far as the applicant knows, provides anunsurpassed efficiency in separating water from oil. The invention willalso result in a correspondingly effective separation of air or othergaseous contaminations from the oil.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in detail with reference to thecorresponding schematic drawings in which:

FIG. 1 is a partial perspective view of an embodiment of the apparatusaccording to the invention;

FIG. 2 is a longitudinal sectional view of a first possible variant ofthe apparatus shown in FIG. 1; and

FIG. 3 is a longitudinal sectional view of a second possible variant ofthe apparatus shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 numeral 2 refers to a vertical, preferably cylindrical closedcontainer or “column” having side wall 4, top wall 6 and bottom wall 8.Spaced below top wall 6, the interior of the column is separated by avertical partition wall 10 into a first section 12 and a second section14, the latter section having a substantially larger cross sectionalarea than that of the first section. The partition wall 10 wouldnormally be in the form of a tube 11 centrally or coaxially arranged inthe column. In the embodiment shown, the interior of tube 11 will thenconstitute the first section 12, while the annular space between tube 11and side wall 4 constitutes the second section 14.

Centrally at the bottom of tube 11, i.e., in the first section 12, thereis an inlet 16 for unprocessed (unseparated) oil, and at the bottom ofthe second section or annular space 14 there is an outlet 18 forprocessed (separated) oil. The inlet 16 is connected, via an inletconduit 20 including a heating element 22 and closing or control valve24, to an oil reservoir (not shown), such as in a lubricating oil systemor hydraulic plant. The outlet 18 is connected, via outlet conduit 26provided with motor 28, to an oil reservoir or tank not shown.

Further, at the bottom of the first section 12 there is a gas inlet 30,preferably in the form of a plurality of nozzles 32 disposed around thecentral oil inlet 16. The gas inlet 32 is, via a gas supply conduit 34,provided with a flow control valve (such as throttle valve) 36 andcleaning/drying filter 38 connected to a gas source 40 which wouldnormally be surrounded by atmospheric air at about 20° C. The top wall 6of container 2, which preferably is dome-shaped, is provided with asuction opening 42 for withdrawing gas and liberated water vapor. Thesuction opening 42 communicates, through a line 43, with a condensingcooler 44, vacuum pump 46 and gas filter 48 discharging to theatmosphere, for example.

Spaced above the first section 12, i.e., above tube 11, there is acircular, substantially horizontal baffle plate 50 having a diameterequal to or somewhat larger than that of tube 11.

In the upper part of the second section or annular space 14 there is anobstruction component 52 having a large surface area serving to impartto the oil flowing across and through the device a correspondingly largesurface facing the upper space 53 of the column. In the example shown inthe figure, the obstruction component 52 is in the form of packing suchas commonly used in columns for evaporation or absorption purposes,supported on a horizontal or slightly downwardly inclined support plate54 extending radially outward from tube 11 toward side wall 6, with asmall gap or clearance 56 between the wall and the edge of the supportplate. The packing, however, covers the cross sectional area of theannular space all the way out to side wall 6. Alternatively, the supportplate 54 could also extend all the way out to side wall 6, and beprovided with perforations permitting oil through-flow.

The operation of the apparatus according to the invention as illustratedin FIG. 1 is as follows.

Vacuum pump 46 is adjusted to provide a vacuum or negative pressure ofat least 0.8 bar in column 2. Upon opening of the oil and gas controlvalves 24 and 36 respectively, the vacuum of column 2 will cause oil andgas (air) to be drawn in through respective inlets 16, 32 at the bottomof tube 11. The inflowing oil is heated by heating element 22 to atemperature which is as high as possible without harming the propertiesof the oil, e.g., about 60° C., while the inflowing air would be atambient temperature such as about 20° C.

As a result of the relatively high vacuum in the column, the inflowingoil (as a first stage of the process according to the invention)together with air which while forming bubbles 32 enters through thenozzles 32, will rise as a turbulent, “effervescent” stream 35 throughtube 11. The air in the bubbles will rapidly be heated to ambient oiltemperature, i.e., a temperature increase of about 40° C., causing thebubbles to expand and thus to achieve a greater surface area orinterference with the oil, while the relative humidity of the bubble airis reduced. Consequently, the air of the bubbles will have a dryingeffect on the oil rising in the inner tube 11 of the column by absorbingthe water in the oil.

Thus, already under this first stage of the separating or dryingprocess, a large proportion of the water contained in the oil will beextracted from the oil.

Owing to its relatively high velocity, the upflowing oil 35 will impactor strike against the baffle plate 50 above tube 11, causing the oil tobe spread out in a radial layer or film 37 through the peripheral gap 33between the baffle plate and the upper edge of the tube while the airbubbles in the oil burst. Thus, the water vapor-containing air isreleased into the upper space 53 of the container 2, and it is withdrawnthrough suction opening 42 as indicated with arrows 39.

Under the action of gravity, the radially flowing oil layer 37 in theupper space 53 of the column (as a second stage of the separatingprocess according to the invention) will fall down over the underlyingobstruction component (which, in this case, comprises packing) andthereby again achieves a very large interface toward the ambient vacuumatmosphere. This results in an effective evaporation of the remainingwater contained in the oil and withdrawal of the water vapor through theopening 42.

Upon having sunk through the packing obstruction component 52, the oilflows outward to the edge of support plate 54 and down through gap 56 asindicated with arrows 41, to be collected in the lower part 58 of thesecond section of the container 14 in a fully processed condition, i.e.,substantially liberated from water.

The above described two-stage process, in which tile oil is caused topresent a continuously large interface toward a space exposed to arelatively high vacuum, will also act to effectively remove possible airor other fluid contaminations in the oil.

The level 60 of the processed oil in the column is adjusted by upper andlower level gauges 62, 64, respectively. When the level reaches theupper level gauge 62, outlet pump 28 is activated to pump oil 43 fromthe column until the pump stops when the oil level reaches the lowerlevel gauge 64.

The water vapor-containing gas withdrawn through opening 42 at the topof the column, is separated from water vapor in condensation cooler 44before reaching the vacuum pump 46, and the exhaust gas from the pump ispreferably cleaned in the gas filter 48 before being released to theatmosphere. Alternatively it could go to a closed exhaust system. Thevacuum in the upper space of the column can be monitored by means of amanometer 66.

The packing obstruction component 52 could be any material commonly usedin chemical engineering for evaporation purposes, such as pall ringsmade of metal or plastics. However, ordinary “marble balls”, i.e., ballsof glass or ceramic material, has been found to be a lowcost andeffective and therefore preferred packing. Normally, about 2,000 ballshaving a diameter of about 16 mm would be suitable.

The container 2 with tubular partition wall 10 could be made of anysuitable material, such as stainless steel. However, a transparent hardplastic, such as plexiglass® is preferred, since it permits observationof the process and adjustment of the oil and air control valves 24, 36in a manner ensuring the most favorable flow conditions for obtaining anoptimum result. More particularly, the valves are preferably adjusteddepending on a predetermined approximate value of the vacuum in thecontainer, as described below in connection with an example of practicaluse of the invention.

The inlet and outlet conduits 20, 26 of the apparatus will normally beconnected to one and the same oil reservoir for continuous operation,such that the oil in the reservoir is maintained in an optimally waterand airless condition. However, the inlet 20 may of course, ifdesirable, be connected to a separate reservoir for unprocessed oilwhile the outlet 28 discharges to another reservoir or tank forprocessed oil.

The dimensions of container 2 will be adjusted to the capacity of theplant to be served by the oil. For an oil reservoir having a capacity ofabout 1,000 litres, the tube 11 can suitably have an inner diameter ofabout 60 mm and a height of about 800 mm, while the diameter and totalheight of container 2 can be about 250 mm and about 500 mm,respectively. The vacuum pump 46 should have a capacity of 20 M³/h, andprovide a maximum vacuum of down to 0.99 bar (1 mbar absolute).

An example of practical use of such an apparatus in the processaccording to the invention for processing oil containing about 2 percentby weight of water (20,000 ppm) and a viscosity of about 32 cSt(32×10⁻⁴m ⅖) is as follows.

With closed oil and air valves 24 and 36 respectively, the vacuum pump46 and heat element 22 is activated. When manometer 66 indicates avacuum of about 0.92 bar, oil valve 24 is opened, permitting oil to flowinto the column owing to the vacuum. The oil valve 24 is adjusted toprovide a flow rate of about 10 l/min. (e.g., by measuring the timeelapsed from the time when the upper level gauge 62 starts outlet pump28 until the lower level gauge 64 stops the pump). When the flow ratereaches the desired value, the vacuum in the column has increased toabout 0.92 bar due to the oil flowing through the column. Now the airvalve 36 is opened and adjusted such that manometer 66 indicates avacuum of between 0.75 and 0.85 bar, preferably about 0.80 bar.Inspection of processed oil from the process according to the aboveexample showed that its content of water was reduced to about 0.08percent by weight (80 ppm). If the oil has a viscosity different fromthat of the above example, different adjustments of the valves may beneeded. Although the valves 24 and 36 according to the above example areadjusted when the process is started, it is of course possible toprovide the valves with a fixed optimum pre-adjustment for a particulartype of oil.

Although the obstruction component 52 for increasing the oil interfacepreferably is in the form of a packing material as described above, itis also within the scope of the invention to use other obstructioncomponents that serve to expose the oil flowing downward in the secondstage of the process to a large surface area. For example, instead ofthe packing shown in FIG. 1, the obstruction component could comprise aplurality of downwardly inclined annular disks 70 as in FIG. 2. Thedisks 70 are arranged one below the other and alternately attached tothe tube 11 and side wall 6 at the respectively inner and outerperiphery thereof, to form gaps 72, 74 with the side wall and tube,respectively, at the opposite peripheral edge of the disks. This willcause the oil to flow “zigzag-like” in a thin layer down along the uppersurfaces of the annular disks 70 before being collected at the lowerpart of the column.

Also in other respects the configuration of the apparatus according tothe invention is not limited to that shown in FIG. 1 and describedabove. Specifically, the first section of the container (i.e., theregion where the oil and gas flow upward during the first stage of theprocess according to the invention) and the second section of thecontainer (i.e., the region where the oil sinks down during the secondstage of the process according to the invention) could be configured inmany different ways. FIG. 3 indicates a variant in which the first andsecond sections are changed around (i.e., inverted) as compared to theembodiment shown in FIG. 1. In the example of FIG. 3, the side, top andbottom walls 4′, 6′, 8′ of container 2′ are substantially similar tothose of the embodiment according to FIG. 1, and the partition wall 10′is again in the form of a central tube 11′. However, tube 11′ has asubstantially larger diameter than that of tube 11 of FIG. 1. Thus, inthis alternative embodiment the relatively narrow annular space betweentube 11′ and column side wall 6′ forms the apparatus first section 12′through which the oil flows up from oil inlet 16′, while the interior oftube 11′ forms the apparatus second section 14′ through which the oil,upon impacting the annular baffle plate 50′, flows down past theobstruction component 52′ (in the case, packing) before being collectedat the lower part of the column and pumped out through the central oiloutlet 18′. The air intake is here preferable in the form of an annularpassage 30′ provided with nozzles.

The column and its two sections need not be cylindrical. Thus, arectangular configuration could be contemplated having a straightpartition wall near one of the side walls, dividing the container in afirst section of small cross sectional area and a second section oflarge cross sectional area.

What is claimed is:
 1. A method of separating water from oil,comprising: heating the oil having the water therein; drawing a vacuumin a container; introducing the heated oil into a first section of thecontainer subjected to the vacuum such that the oil flows upward throughthe first section due to the vacuum; introducing a gas into the oil inthe first section of the container such that gas bubbles rise throughthe oil so as to absorb water vapor from the oil; removing the gashaving the water vapor from a top portion of the container; introducingthe oil into a second section of the container from the first section ofthe container, the second section having an obstruction componenttherein, wherein the oil is introduced into the second section so as toflow downward through the second section and spread around theobstruction component such that the surface area of the oil isincreased; and collecting the oil in a bottom portion of the secondsection of the container.
 2. The method of claim 1, wherein the heatedoil is introduced with the gas into a bottom portion of the firstsection of the container.
 3. The method of claim 2, wherein the gascomprises ambient, non-preheated atmospheric air.
 4. The method of claim2, wherein said heating of the oil comprises heating the oil to 60° C.5. The method of claim 2, wherein said drawing of a vacuum in thecontainer comprises drawing a vacuum of at least 0.8 bar.
 6. The methodof claim 5, wherein said drawing of a vacuum in the container comprisesdrawing a vacuum of 0.85 bar.
 7. The method of claim 5, wherein saidheating of the oil comprises heating the oil to 60° C.
 8. The method ofclaim 5, wherein the gas comprises ambient, non-preheated atmosphericair.
 9. The method of claim 1, wherein said drawing of a vacuum in thecontainer comprises drawing a vacuum of at least 0.8 bar.
 10. The methodof claim 9, wherein said drawing of a vacuum in the container comprisesdrawing a vacuum of 0.85 bar.
 11. The method of claim 9, wherein saidheating of the oil comprises heating the oil to 60° C.
 12. The method ofclaim 9, wherein the gas comprises ambient, non-preheated atmosphericair.
 13. The method of claim 1, wherein said heating of the oilcomprises heating the oil to 60° C.
 14. The method of claim 13, whereinthe gas comprises ambient, non-preheated atmospheric air.
 15. The methodof claim 1, wherein the gas comprises ambient, non-preheated atmosphericair.
 16. An apparatus for separating water from oil, comprising: acontainer having a water-containing oil inlet, an oil outlet, a gasinlet for introducing gas into the water-containing oil in thecontainer, a gas outlet for withdrawing gas having water vapor from atop portion of the container; a substantially vertical partition wallarranged in an interior of said container below said gas outlet so as todivide said interior of said container into a first section and a secondsection, said water-containing oil inlet and said gas inlet beinglocated at a bottom portion of said first section, said oil outlet beinglocated at a bottom portion of said second section; a baffle platespaced above said first section of said container for directing a flowof the oil to be introduced into said first section by saidwater-containing oil inlet from a top portion of said first section intosaid second section; and an obstruction component at a top portion ofsaid second section for spreading out the oil directed into said secondsection so as to increase a surface area of the oil.
 17. The apparatusof claim 16, wherein said partition wall comprises a tube arranged alonga longitudinal central axis of said container.
 18. The apparatus ofclaim 17, wherein said first section of said container comprises aninterior of said tube.
 19. The apparatus of claim 17, wherein saidsecond section of said container comprises an interior of said tube. 20.The apparatus of claim 16, wherein said obstruction component comprisespacking material.
 21. The apparatus of claim 20, wherein said packingmaterial comprises a plurality of marbles.
 22. The apparatus of claim21, wherein each of said marbles is formed of one of glass material andceramic material.
 23. The apparatus of claim 17, wherein saidobstruction component comprises a plurality of annulardownwardly-inclined disks alternately fixed to an outer surface of saidtube and an inner surface of said container.